Surface Degradation of Thin-Layer Al/MgF Mirrors under Exposure to Powerful VUV Radiation.

Thin-layer Al/MgF coatings are currently used for extraterrestrial far-UV astronomy as the primary and secondary mirrors of telescopes (such as "Spektr-UF"). Successful Hubble far-UV measurements have been performed thanks to MgF on Al mirror coatings. Damage of such thin-layer coatings has been previously studied under exposure to high-energy electrons/protons fluxes and in low Earth orbit environments.